C8 IDENTIFICATION OF IONS BY Name: ________________________ CHEMICAL AND SPECTROSCOPIC MEANS Class: ________________________ Question Practice Date: ________________________ Time: 164 minutes Marks: 163 marks Comments: GCSE CHEMISTRY ONLY Immanuel+College Page 1 of 60 This question is about reactions of ethanoic acid and the analysis of salts. 1 (a) Figure 1 shows the apparatus used to investigate the reaction of ethanoic acid with calcium carbonate. (i) Describe a change that would be seen in each test tube. Give a reason for each change. Test tube 1 ____________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ Test tube 2 ____________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ (4) (ii) Complete the displayed structure of ethanoic acid. (1) Immanuel+College Page 2 of 60 (iii) Ethanoic acid is a carboxylic acid. Complete the sentence. Carboxylic acids react with alcohols in the presence of an ____________ catalyst to produce pleasant-smelling compounds called ______________ . (2) (b) Figure 2 shows four test tubes containing three different salt solutions and water. Each solution and the water was tested with: • silver nitrate in the presence of dilute nitric acid • barium chloride in the presence of dilute hydrochloric acid. Complete the table of results. Calcium Potassium Ammonium nitrate Water chloride solution sulfate solution solution Test with silver nitrate in the no change no change presence of dilute nitric acid Test with barium chloride in the no change white precipitate presence of dilute hydrochloric acid (2) Immanuel+College Page 3 of 60 (c) Flame tests can be used to identify metal ions. (i) Complete the following sentences. The flame colour for potassium ions is ____________ . The flame colour for calcium ions is ____________ . (2) (ii) Give one reason why a flame test would not show the presence of both potassium ions and calcium ions in a mixture. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ (1) (Total 12 marks) Cheshunt mixture is a powder containing copper sulfate, CuSO , and ammonium carbonate, 2 4 (NH4)2CO3 (a) A student tested the Cheshunt mixture. (i) Hydrochloric acid was added. A gas was produced that turned limewater milky. Complete the sentence. The gas was __________________________________ which shows that _________________________ ions are in the mixture. (2) (ii) Sodium hydroxide solution was added. A gas was produced that indicates that ammonium ions are in the mixture. Complete the sentence. The gas was __________________________________ which turns damp red ___________________________________________ blue. (2) Immanuel+College Page 4 of 60 (b) Cheshunt mixture is dissolved in water before it is used. When the student dissolved the Cheshunt mixture in water it formed a blue solution. (i) Suggest how the student knew that copper ions are in this solution. ______________________________________________________________ ______________________________________________________________ (1) (ii) The student tested the Cheshunt solution and the result of the test indicated that sulfate ions are in the solution. Complete the sentence. The student added a solution of ________________ in the presence of dilute hydrochloric acid and a ________________ precipitate was produced. (2) (Total 7 marks) 3 Read the information in the box and then answer the questions. Seidlitz Powder is the name of a medicine. Seidlitz Powder comes as two powders. One powder is wrapped in white paper and contains tartaric acid (C4H6O6). The other powder is wrapped in blue paper and contains potassium sodium tartrate (KNaC4H4O6) and sodium hydrogencarbonate (NaHCO3). The contents of the blue paper are completely dissolved in water and then the contents of the white paper are added. The equation which represents this reaction is: + 2NaHCO (aq) Na C H O (aq) + 2H O (l) + 2CO (g) C4H6O6 (aq) 3 2 4 4 6 2 2 (a) Describe and give the result of a test to identify the gas produced in this reaction. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ (2) Immanuel+College Page 5 of 60 (b) One of the chemicals in Seidlitz Powder is potassium sodium tartrate (KNaC4H4O6). Suggest why it would be difficult to identify both potassium ions and sodium ions in potassium sodium tartrate using a flame test. ___________________________________________________________________ ___________________________________________________________________ (1) (c) Some Seidlitz Powder was bought on the Internet. However, when tested, it was found to be only magnesium sulfate. (i) Describe and give the result of a chemical test to show that magnesium sulfate contains sulfate ions. Test __________________________________________________________ ______________________________________________________________ Result ________________________________________________________ ______________________________________________________________ (2) (ii) Magnesium sulfate contains magnesium ions. Describe what you see when sodium hydroxide solution is added to a solution of magnesium sulfate. ______________________________________________________________ ______________________________________________________________ (1) (Total 6 marks) Immanuel+College Page 6 of 60 Read the information about protecting the bottoms of ships. 4 A Copper-bottomed Investment From the 16th to the 19th century, the bottoms of many wooden ships were protected from marine organisms by being covered with sheets of metal. At first lead was used on the bottoms of ships, then copper was used until 1832 when Muntz Metal replaced it. Muntz Metal is an alloy of two transition metals, copper and zinc. Table of data Lead Copper Muntz Metal Cost (£/kg) £1.20 £3.20 £2.30 Melting point (°C) 327 1083 904 Stops sea worms attacking wood Yes Yes Yes Stops barnacles and seaweed No Yes Yes sticking to the bottom of the ship (a) Use the information to answer the following questions. (i) Suggest why copper replaced lead. ______________________________________________________________ ______________________________________________________________ Immanuel+College Page 7 of 60 (1) (ii) Suggest why Muntz Metal replaced copper. ______________________________________________________________ ______________________________________________________________ (1) (b) A sample of Muntz Metal contains a very small amount of iron as an impurity. (i) Name an instrumental method of analysis that could be used to detect iron. ______________________________________________________________ (1) (ii) Suggest why an instrumental method would detect the iron in this sample of Muntz Metal but a chemical method is not likely to be successful. ______________________________________________________________ ______________________________________________________________ (1) (c) Today, ships are made from steel. Steels are alloys of iron, a transition metal. Give two properties of transition metals that make them suitable for making ships. Property 1 __________________________________________________________ ___________________________________________________________________ Property 2 __________________________________________________________ ___________________________________________________________________ (2) (Total 6 marks) Immanuel+College Page 8 of 60 Alums are salts. They have been used since ancient times in dyeing and medicine and still have 5 many uses today. Three alums are shown in the table: Name Ions present + 3+ 2- Ammonium alum NH4 Al SO4 + 3+ 2- Potassium alum K Al SO4 + 3+ 2- Sodium alum Na Al SO4 2- (a) These alums contain sulfate ions (SO4 ). Describe and give the result of a chemical test to show this. Test _______________________________________________________________ ___________________________________________________________________ Result _____________________________________________________________ ___________________________________________________________________ (2) (b) These alums contain aluminium ions (Al3+). Describe how sodium hydroxide solution can be used to show this. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ (2) Immanuel+College Page 9 of 60 (c) Aluminium ions do not give a colour in flame tests. However, flame tests can be used to distinguish between these three alums. Explain how these three alums could be identified from the results of flame tests. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________